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sound amplification

Discussion in 'General Electronics Discussion' started by hexe, Oct 17, 2011.

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  1. hexe

    hexe

    3
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    Oct 9, 2011
    I need to record some enviromental sounds (not speech).I tried my pc's microphone but it cannot even record sounds i can hear without any device.I want to hear barely noticable sounds loudly.Sound quality and distortion is not that important.Mic wil be used indoors and sounds will be recorded to pc.Can you offer me any simple solutions.I dont know much about electronics.I can make a pcb if you send schematics or simple things like that.Thanks
     
  2. alfa88

    alfa88

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    5
    Dec 1, 2010
    Recording Sounds

    Assuming you have a PC and a built in microphone you need to select the microphone as the recording source and make sure it isn't muted. Double click on the speaker to get to the settings panel or look in the control panel.
     
  3. new_hope

    new_hope

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    Oct 22, 2011
    I dont think its gonna be that simple. You may need a better mic. Audible human voice is in the 3000mhz range and under (via avr amtel document describing how to program an mcu to pick up human voice). If you are wanting to pick up sounds that are not audible to human ears then you will need a mic designed to pick them up. Your computer mic is there to recognize human audible voice and human audible sounds.

    even if it was to pick them up you would only be able to detect them via a frequency graph of the sound or if they were converted into human audible sounds...which would essentially make them completely different from there original sound.

    Thats like trying to press a microphone to a wall to here conversations in a room opposite to the wall. They have technologies that can do this (or maybe it was just in the movie i saw lol)....but it is designed to be applicable to those situations only.
     
  4. hexe

    hexe

    3
    0
    Oct 9, 2011
    I can hear these sounds without any device.They are bearly noticable because my mic cannot pick them.

    I want to record footsteps or more accurately people on the stairs of my apartment.An audio detection software (like a motion detection software for a wabcam) will email me recordings whenever it detects someone so that i will know if someone is waiting for me inside the building.It may sound paranoid but there were some incidents around here lately.

    I bought a cheap microphone and made some recording with audacity software

    audacity software (to open the recording):

    http://audacity.sourceforge.net/ .

    recording:

    http://www.2shared.com/file/uvcP35JD/1_online.html

    Recording is amplified with 35db gain.My flat is on the second floor.In the recording i descended to the ground floor (at about 38th second) and then began climbing.

    I want to be able to hear footsteps two floors up and down.For clearer and much more louder recording what do you advice?

    specifications of the microphone i used for recording:

    omni-direction
    output impedance:1.4k+-30%

    frequency response:50~16khz

    sensitivity:-58db+-2db

    operating voltage:1v~10v

    current consuption:0.8ma max

    s/n ratio 40db or more
     
    Last edited: Oct 22, 2011
  5. new_hope

    new_hope

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    Oct 22, 2011
    I dont really know all the specifics on frequency of sound, impedance of mics, and decibels given off by various sounds. I just know that human audible voice is below 3000 something hz because i read an amtel document that was describing how to record audio with a AVR MCU in the most efficient manner when a mic was connected to it. I have it bookmarked.

    The thing with audacity is it is commercial software that can't be interfaced in real time...what im getting from your own words at least. I'm assuming you want it to alert you in real time when footsteps or other sounds are heard in the hallways to signal human presence. That software would only let you detect it from pre-recorded audio....in your own words at least.

    You would most likely need to write your own c++ script with open source libraries (I'm actually trying to find one that allows you to access live audio feeds in real time and run computations on them). This could be rather advanced as you would have to program it to ignore common sounds or only alert you once the sound is heard multiple times. But would be made easier when you had visible audio soundwave graph's.

    I could make it display the soundwave graph with opengl. But i wouldn't know how to accurately determine what sound are in what frequency unless i found an opensource library that allowed more advanced function rather then just playing and pausing an audio file. Which i haven't yet found.
     
  6. hexe

    hexe

    3
    0
    Oct 9, 2011
    Sorry for late reply

    Yes audacity doesnt work in real time and i couldnt find any real time amplifying software.I will use zonetrigger http://www.zonetrigger.com/sound-detection/.It records those sounds it detects.I will connect to my pc remotely to listen its recordings.To amplify sounds i am thinking of building a preamplifier circuit but dont know which one is suitable for me.Any advice?

    Thanks
     
    Last edited: Oct 27, 2011
  7. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    I am gonna go out on a limb here and say that any microphone that can pick up footsteps 2 floors away is also gonna pick up noise made by you a lot less then 2 floors away. I don't see how you are gonna distinguish the sounds you want from the sounds you don't.
     
  8. davenn

    davenn Moderator

    13,865
    1,956
    Sep 5, 2009
    Agreed. altho it sounds as tho its mainly for use when the Op isnt in the apartment. just a warning to if some one else is.

    Then you really need a mic or other sensor in direct contact with those stairs.
    else other enviro. sounds are likely to mask the wanted sounds

    in direct contact means the mic etc will pick up every tiny bump and squeek of the steps :)

    Dave
     
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